The Doctrine of Double Effect

In my recent post on euthanasia, a thought experiment was mentioned which I’d like to address at greater length:

In one dilemma, you are standing by a railroad track when you notice that a trolley, with no one aboard, is heading for a group of five people. They will all be killed if the trolley continues on its current track.

The only thing you can do to prevent these five deaths is to throw a switch that will divert the trolley onto a side track, where it will kill only one person. When asked what you should do in these circumstances, most people say that you should divert the trolley onto the side track, thus saving a net four lives.

In another dilemma, the trolley, as before, is about to kill five people. This time, however, you are not standing near the track, but on a footbridge above the track. You cannot divert the trolley. You consider jumping off the bridge, in front of the trolley, thus sacrificing yourself to save the five people in danger, but you realize that you are far too light to stop the trolley.

Standing next to you, however, is a very large stranger. The only way you can prevent the trolley from killing five people is by pushing this large stranger off the footbridge, in front of the trolley. If you push the stranger off, he will be killed, but you will save the other five. When asked what you should do in these circumstances, most people say that it would be wrong to push the stranger.

The conclusion that most people draw is that it is acceptable to throw the switch, but not to push the fat man onto the tracks. This argument is usually raised as an insuperable dilemma for utilitarianism, since in both cases the overall outcome (one person dies, five survive) is the same. Utilitarian reasoning would seem to consider both scenarios equivalent, yet most people feel very strongly that they are not the same.

The original commenter who raised this dilemma suggested, as others have, that this is evidence for the evolutionary origin of morality. The usual argument along these lines is that directly pushing another person into harm’s way is something that could have happened in our species’ past, and therefore our brains are primed to respond emotionally to it. Pulling a lever, however, is an action that nothing in our evolutionary heritage prepared us for. Therefore, we do not feel the same instinctive reaction of emotional repulsion, which leads most people to conclude that the first scenario is somehow more acceptable than the second.

Although I am a utilitarian (more specifically, a universal utilitarian), I believe that it’s allowable to pull the lever, but not to push the man onto the tracks. I’ll explain why in a moment, but first I’d like to make an observation. We didn’t have levers in our ancestral environment. But we also did not have trains. If people don’t have as strong a moral reaction to things we didn’t grow familiar with over millions of years, why do people show any emotional response to any of the train scenarios at all? If this reasoning was correct, shouldn’t our evolved minds not “grasp” the danger an onrushing train poses, and shouldn’t people react impassively to all versions of the train scenario? Clearly that is not the case.

I think there’s a superior explanation that illuminates the key difference between the two scenarios, and it’s this difference that most people intuitively grasp. The difference comes from a famous moral principle, the doctrine of double effect:

…sometimes it is permissible to cause such a harm as a side effect (or “double effect”) of bringing about a good result even though it would not be permissible to cause such a harm as a means to bringing about the same good end.

As the doctrine of double effect tells us, it is intent that makes all the difference. A person who shoots and kills someone else at random, in cold blood, is a murderer; a person who shoots and kills someone who was attempting to kill them is not a murderer, but has merely acted in justifiable self-defense, though the end result is the same. Likewise, if our country was at war with another, deliberately bombing a residential area in the enemy country to kill civilians and create panic and terror among the survivors would be a war crime. However, bombing a factory used to manufacture munitions for the army is a legitimate tactic of warfare, even if civilians work there and the bombing kills just as many of them. And the same is true of the trolley scenario. It is the difference between unwanted but unavoidable harm, versus foreseen and intended harm, that is the key distinction between the two. (This applies in the other direction as well: a man who shoots at the President, intending to assassinate him, is no less culpable if his bullet misses its target.)

The only question is whether a utilitarian moral system can recognize the importance of intent, and I have always firmly supported the position that universal utilitarianism can do this. UU’s fundamental counsel is that we should judge our actions not just by the real harm they actually produce, but by the potential harm they might produce – in other words, by the intent of the actor.

In the trolley scenario, a person who acts with the intent to kill one person in order to save others has introduced a vast amount of potential suffering – as in the scenario where a healthy person is vivisected so that their organs can be given to the seriously ill, it raises the chilling scenario of a ruthless society where anyone’s life may be ripped away at any time without their consent in order to be used as a means to an end. No one could live happily in a society where such acts were the norm. The other trolley scenario, where the one’s death is unintended but unavoidable, also introduces some potential suffering, but much less. It gives all people the proper assurance that their lives are valuable, that they will not be callously killed without notice to serve the interests of a stranger. Only in a society that shows this basic degree of respect for human life could the stability exist that makes happiness possible.